Field of the Invention
The present invention relates to a light source apparatus, a method for controlling the light source apparatus, and a display apparatus.
Description of the Related Art
Some color image display apparatuses comprise a color liquid crystal panel having a color filter, and a light source apparatus (backlight apparatus) that irradiates white light onto the back face of the color liquid crystal panel.
Conventionally a fluorescent lamp, such as a cold cathode fluorescent lamp (CCFL) has primarily been used as a light source of a light source apparatus. Recently however light emitting diodes (LEDs) have begun to be used for a light source of a light source apparatus because of excellence in terms of power consumption, product life, color reproduction and environmental impact.
The light source apparatus that uses LEDs as the light source (LED backlight apparatus) normally has many LEDs. Japanese Patent Application Laid-Open No. 2001-142409 discloses an LED backlight apparatus having a plurality of emission units each of which having one or more LED(s). Japanese Patent Application Laid-Open No. 2001-142409 also discloses that the brightness is controlled for each emission unit. By dropping the emission brightness of the emission unit that irradiates light onto an area where dark images are displayed, out of a screen of a color image display apparatus, power consumption decreases and contrast of the image improves. This kind of brightness control for each emission unit according to the characteristic of the image is called “local dimming control”.
One problem of a light source apparatus is the change of emission brightness of the light emitted from an emission unit. For example, the emission brightness changes by the change of emission characteristic of the light source depending on the temperature change, or by age deterioration of the light source. In the case of an emission apparatus having a plurality of emission units, dispersion of emission brightness (unevenness of brightness) is generated in a plurality of emission units because of the dispersion of the temperature values and degree of age deterioration among the plurality of emission units.
As a technique to decrease such changes of the emission brightness and unevenness of brightness, a technique of adjusting the emission brightness of the emission units using an optical sensor is known. In concrete terms, an optical sensor that detects reflected light, which is light emitted from the light source apparatus, reflected by an optical sheet (optical member) of the light source apparatus and returned to the emission unit side, is located, and the emission brightness of the emission unit is adjusted based on the detected value by the optical sensor. In an emission apparatus having a plurality of emission units, each emission unit is turned ON sequentially, and the reflected light is detected by an optical sensor for each emission unit, and the emission brightness is adjusted. This technique is disclosed in Japanese Patent Application Laid-Open No. 2011-27941.